1. Field of Invention
The invention relates to a method of calibrating a test chart and a scanning device, and more particularly to a method of calibrating a scanning device and a test chart which is formed by way of printing.
2. Related Art
A conventional scanner has to be calibrated before the scanner is shipped out. The optical properties of the scanner, such as the luminance distribution property of a light source of the scanner, the sensitivities of an image sensor of the scanner or a combination thereof, may be calibrated according to a standard reference test chart. The scanned image is free of distortion after this calibration work has been done.
FIG. 1 is a schematic illustration showing a conventional test chart. In order to manufacture a conventional test chart 100, several photographs of different optical densities (ODs) are developed and printed. Then, the photographs are cut into several blocks 111 to 116, which are then adhered to a base plate 110. However, four corners (or at least one corner 112A) of each of the blocks 111 to 116 tend to raise from the base plate 110 after a period of time, thus failing to provide a standard test chart for the calibration of the scanner. In addition, the cost of manufacturing one conventional test chart is very high, around 330 U.S. dollars, and not suitable for mass production.
So, the conventional test chart cannot be adapted to be used in the calibration of the sheet-fed scanner.